The Twelve Apostles are the Great Ocean Road's unavoidable icon: limestone stacks standing just offshore, cut by surf from the retreating cliffs. They are spectacular, even with the crowds, especially when low sun turns the stone gold.
The main viewing platforms are easy and heavily managed. Go at sunrise or sunset if you can, and do not obsess over the exact number of stacks; the power of the place is the ongoing collapse and reshaping of the coast.